The present invention relates to improvements in exhaust manifolds, and in particular to a moisture inhibitor system for wet exhausts as utilized in marine applications such as boats and other watercraft.
The preferred embodiment of the present invention contemplates an exhaust manifold having an inner exhaust passage which has situated therein a collection barrier or raised pocket situated to collect moisture migrating from the exhaust port, generally at the stern of the vessel.
The collection pocket is heated by the exhaust stream, and is formed to collect and retain the migrating moisture, while simultaneously evaporating (via stored heat from the exhaust stream) the collected moisture forming moisture vapor, which moisture vapor is urged by the exhaust stream through the exhaust passage and the exhaust port, where it leaves the system. The system thereby prevents moisture migrating up the exhaust passage from reaching the engine. The collection pocket is configured so as to provide minimal disturbance in the flow of exhaust through the system.
In the preferred embodiment of the invention, the exhaust pipe includes a generally vertical portion emanating from the engine, and an elbow at the top of the vertical portion communicating with an exhaust conduit situated generally horizontally, but with a slightly downwardly angled path leading to the exhaust port at the stern of the vessel. In this embodiment, the moisture collection pocket is situated in the lower inner portion of the generally horizontal exhaust conduit, in the vicinity of the elbow.
An alternative embodiment of the present invention contemplates a moisture collection pocket formed inside portion of the manifold elbow adjacent to the manifold opening at the engine head.
Inboard marine engines, as utilized in smaller boats and yachts generally vent exhaust from the engine through the stern of the vessel. Such venting is not without the potential for problems, particularly when a vessel is underway at low speed/low RPM""s, when the vessel quickly reduces speed or stops, and when a vessel is idling. During such conditions, moisture droplets are prone to enter the stern exhaust passage and migrate up the exhaust conduit to the manifold, where said moisture (often salt water) can enter the engine and damage same.
Such moisture entry into the exhaust system (hereinafter referred to as xe2x80x9creverse migration) can be due to the water physically washing up against the stern, and/or can be blown into the vicinity of the stern exhaust via the xe2x80x9cstation wagon effectxe2x80x9d when the vessel is underway. The compression stroke of an internal combustion engine, particularly one which is not perfectly tuned, can include a somewhat substantial, yet brief, suction during the exhaust cycle, which suction can draw liquid moisture through the exhaust conduit to the engine head if left unchecked. Such exhaust migration to the head of the engine can destroy the engine over time, especially when the water contains salt.
Prior art systems have attempted various solutions to prevent this very problem, including, for example:
U.S. Pat. No. 5,133,185 entitled Anti Moisture Device for Engine Exhaust teaches (see FIG. 3) a lip situated at the exhaust connection to the engine to block moisture droplets travelling upstream into the exhaust duct, so as to prevent the droplets from entering the engine. It is readily noted that the ""185 system is only useful for blocking relatively small amounts of moisture, the capture area formed by the lip being relatively small. If said capture area, shown as a hollow truncated conical shape, were to fill with moisture, any additional moisture would spill over directly into the head of the engine, causing catastrophic damage.
U.S. Pat. No. 4,589,852 teaches a rather complex system of baffle walls configured to allow the exhaust venting of gases from a marine engine therethrough, while preventing moisture from the riser from entering the engine. Such a configuration would represent a significant cost, may reduce performance of the engine due to unnecessary exhaust turbulence, and would require space within the vessel for placement and servicing; in a vessel such space is at a premium.
U.S. Pat. No. 4019456 issued 1977 teaches a wet exhaust system designed to prevent moisture from migrating into the system via the xe2x80x9cstation wagon effectxe2x80x9d created when a vessel is in forward motion.
As may be discerned by a review of the above, prior art systems for preventing moisture migration in marine exhaust may be considered to have been somewhat limited in their ability to process other than small amounts of moisture, or were rather bulky and expensive to implement and maintain.
Unlike the prior art, the present invention provides an anti-moisture system to prevent the reverse migration of moisture fluid through an exhaust conduit which is compact, effective, reliable, relatively inexpensive, and which requires little in the way of maintenance.
The present invention seeks to block the reverse, upstream migration of moisture fluid from the stern of the vessel through the exhaust conduit, by providing an exhaust capturing pocket monolithically formed (in the preferred embodiment) as part of the manifold, wherein the moisture is collected, and the heat conducting metal forming the pocket and conduit quickly evaporates the collected moisture, forming moisture vapor, which is vented via the exhaust stream from the stern of the vessel.
In accomplishing this task, a system is illustrated wherein there is provided therein an internal combustion engine having a exhaust vent or manifold, the exhaust conduit forming the manifold then bending to form an elbow which directs the flow of exhaust, via a conduit, to the stern of the vessel.
Formed within in the exhaust conduit adjacent to the upper portion of the elbow, at the base of the inner wall of the conduit is a raised collection pocket having a containment aid area facing upstream of the exhaust, the collection pocket configured to collect fluid moisture creeping along the lower portion of the exhaust conduit and flash evaporate same to a vapor, where it may be vented from the vessel via the exhaust stream. The configuration and placement of the collection pocket maximizes collection of the fluids, while minimizing disturbance of exhaust gas flow from the engine.
An alternative embodiment of the present invention, which may be used separately or in concert with the preferred embodiment, contemplates collection pocket formed at the base of the exhaust manifold, within the elbow, providing a collection compartment within the exhaust manifold itself adjacent to the exhaust vent at the head of the engine.
It is therefore an object of the present invention to provide a system for preventing the reverse migration of water in an exhaust manifold.
It is another object of the present invention to provide a collection system for collecting, evaporating, and venting moisture in an exhaust manifold which may be utilized with a variety of marine exhaust systems.
It is another object of the present invention to provide a liquid collection system in marine exhaust manifolds, and method therefore, which is inexpensive to manufacture, reliable in operation, and space efficient upon implementation.
Lastly, it is an object of the present invention to provide a system for collecting and removing liquids from an exhaust manifold which may be retrofitted to existing exhaust systems.